LONDON  Some Americans here confess to keeping quiet in public so no one can hear the telltale accent of their homeland.

Others, fearful of attacks on this city's famed underground transport system, said they have stopped taking the tube.

The American, a newspaper for U.S. expatriates living in Britain, no longer prints meeting places and times for social and business groups.

These are frightening times for the more than 2 million Americans living abroad and beyond the protective reach of U.S. law enforcement. Already skittish after the terrorist attacks in the United States four weeks ago, their fears were ratcheted up after missile and bombing strikes against targets in Afghanistan began Monday.

After the attacks, the State Department cautioned that U.S. citizens abroad should be prepared for "strong anti-American sentiment and retaliatory actions."

In Indonesia, the largest Muslim country, Americans were told this week to be ready for evacuation. Foreign schools there closed, and the U.S. and Australian embassies told their citizens to stay home.

Schools catering to foreign children in at least six other Arab and Muslim states  Bahrain, Egypt, Oman, Qatar, Saudi Arabia and Syria  also were closed Monday, according to embassy messages posted on the Internet.

U.S. intelligence officials have warned Congress that, in addition to the threat of generic anti-American protests, terrorists associated with Osama bin Laden could launch attacks against Americans and American businesses and government institutions abroad.

"People are talking about whether Pakistani nuclear weapons could reach London. They worry about traveling on the tube. They won't speak in public, so they aren't recognized by their American accents," said Marcia Balisciano, who works with British-American Business Inc. "It's clearly affecting our community here."

Britain, and London in particular, are considered by many to be ripe for a terrorist attack, partly because of the high profile that Prime Minister Tony Blair has taken in supporting the United States and the global anti-terrorism coalition it has mounted.

With nearly 300,000 Americans living here, the United Kingdom is home to more Americans than any other foreign country.

The British government has added 1,500 police to the streets, including extra foot patrols, and the subway has added staff to reassure passengers. A London Underground spokeswoman said ridership was down slightly, but that was likely because of a drop in tourism.

High-visibility security has been stepped up at several potential targets, including Buckingham Palace and Downing Street, where the prime minister lives.

Many U.S. employers have pulled their staff out of the Persian Gulf and Pakistan. General Motors, for example, has at least temporarily relocated all Americans working in Dubai in the United Arab Emirates to Frankfurt, Germany.

At the Lahore American School in northeastern Pakistan, all 28 expatriate teachers and all but two of the 50 foreign students have been evacuated.

Meanwhile, many Americans abroad are trying to keep a low profile, or even conceal their ties to the USA:

 The London branch of California-based Pepperdine University has taken down its American flag, as well as signs that identify the main campus as in Malibu. In addition, a security guard has been hired for the first time. "For the parents, of course, not the students," says Colleen Graffy, academic director in London.

 In northern Italy, the American Aviano Air Base is considering putting Italian license plates on military vehicles. "It has been considered for some time as part of an effort to blend in with the community," said base spokeswoman Capt. Erina Dick. "Now, after the attacks, the process has been accelerated."

 U.S. troops in South Korea are being encouraged to wear civilian clothes when they venture off base so they can't be so easily identified. The military bases, where some 37,000 American troops are stationed, have imposed a curfew and barred soldiers from going to nightclubs and bars.

"It all boils down to something very simple: Do you want to identify yourself as belonging to any nationality in particular?" said Tim Davies, regional director of business development for the Hong Kong office of Kroll, a security company. "The simple fact at the moment is, you don't."

Adds Edward Pressman, an executive in Jakarta, Indonesia, with a U.S.- based multinational company: "I keep a low profile. I don't engage in political debate with people I don't know. I don't take the same route to work every day."

While many refuse to be cowed by the potential of being targeted for further terrorist strikes  or even the risk of being taken hostage, as some law enforcement authorities have suggested might happen  almost everybody is more cautious.

"There's not really a whole lot you can do, but you can reduce the chances that the 'opportunists' have," said Cheryl Powell, editor of The American, a 41,000-circulation monthly newspaper in Britain.

Where her newspaper previously printed contact telephone numbers and addresses in the calendar, now only an event and date are listed. Likewise, social events where large numbers of Americans might gather, such as the Thanksgiving dinner sponsored by the American Women's Club, are not being widely advertised.

Foreign schools and American study-abroad programs here are re-examining their evacuation programs  largely to reassure parents, said Rachel Valladares, who runs internship programs for U.S. students studying in London.

"But we are telling kids to tone it down," Valladares says. "Don't sing the Star Spangled Banner when you walk down the street. There's a lot of anti-Americanism here."